Fuel pump for internal-combustion engines



Sept. 28 1926. 1,601,345

.E. R. BURTNETT FUEL. PUMP FOR INTERNAL COMBUSTION ENGINES Filed A ril 17, 1924 V 7 Z 't/ ll u| Patented Sept. 28, 1926.

UNITED STATES PATENT OFFICE.

EVERETT R. BURTNETT, OF LOS ANGELES, CALIFORNIA, ASSIGNOR, BY DIRECT AND MESNE ASSIGNMENTS, TO THE AUTOMOTIVE VALVES 00., OF LOS ANGELES, GALI- FORNIA, A VOLUNTARY TRUST.

FUEL PUMP FOR INTERNAL-COMBUSTION ENGINES.

Application filed April 17, 1924. Serial No. 707,102.

My invention relates to internal combusion engines of the two stroke cycle type and aaving a pumping cylinder that functions for the precompressing and pumping of gaseous fuel into a combustion cylinder, the principal objects of my invention being to provide relatively simple and efficient valvular means for controlling the admission of gaseous fuel into the pumping or precompression cylinder, which valvular means includes two inlet valves and their actuating parts including cams; to provide for a simultaneous actuation of the valves by separate cam lobes on the cam shaft; to provide a construction wherein the operation of the cam shaft is at one-half the engine or crank shaft speed, and further, to provide a relatively simple construction that will be effective in bringing about a material reduction of valve spring tensionwith resultant longer lived valves and earns; to bring about silence of operation; to provide for increased port area and to effect a material increase in power, as a result of the'complete closing of the inlet valves, after each opening or gaseous fuel inlet action.

With the foregoing and other ObJEO'CS in view, my inventlon consists in certain novel features of construction and arrangement of' parts that will be hereinafter more fully described and claimed and illustrated in the accompanying drawings in which:

Fig. 1 is a verticalsection taken lengthwise through the axis of the pumping or precompression cylinder of a two stroke cycle engine and showing the same equipped with my improved gaseous fuel inlet control valves.

Fig. 2 is a vertical section taken on the line 22 of Fig. 1.

Fig. 3 is a perspective view of the valve actuating cams.

Referring by numerals to the accompanying drawings which illustrate a practical embodiment of my invention, 10 designates the pumping or precompression cylinder of a two stroke cycle internal combustion engine, which cylinder forms a part of a block that surmounts a crank case 11 and arranged for reciprocatory movement within said cylinder is a gaseous fuel pumping or precompression piston 12.

i A crank shaft 13 is journalled in. suitable bearings in crank case 11 and. connecting piston 12 to one of the cranks of said shaft is-an ordinary connecting rod 14.

The head end of the cylinder block is closed by a plate or head block 15, and formed in the under face thereof, is a shallow recess or pocket 16. Leading from one side of this pocket, outwardly through the side of head block 15, is a short outlet duct 17, for the precompressed'gaseous fuel and directly connected to'this' outlet duct is one end of a transfer duct 18, that leads to the chamber of a combustion cylinder (not shown). v

Onthe side opposite from outlet duct 17, recess 16 is provided with a laterallye-xtending pocket 19 that overlies and'com-' municates directly with the upper end of a gaseous fuel inlet duct 20, that is formed in the side and upper portion of the cylinder block to the side of the pumping cyl inder 10.

This duct 20 is suitably connected to a source of gaseous fuel supply, for instance, a carburetor (not shown).

The upper end of this inlet duct terminates in a pair of circular openings 21 that are formed so as to provide seats for a pair of poppet valves 22.

The stems 23 of these valves reciprocat through suitable bearings 24 and the lower portion of each stem is equalized with an expansion spring 25 that exerts pressure to normally hold the valve upon its seat.

The lower. ends of the valve stems are adapted to be engaged by the upper ends of short push rods or plungers 26 that operate in suitable bearings 27. The lower ends of the plungers 26 bear directly on the periphcries of cams 28 that are fixedly mounted upon a cam shaft 29, that is journalled in suitable bearings in the upper portion of crank case 11. Each cam has a pair of lobes 30, the members of each pair being arranged diametrically opposite to each other or 180 degrees apart. The two cams occupy the same relative position upon the cam shaft, so that as the latter makes one complete revolution, each cam having two lobes will be effective in lifting and opening the corresponding valve twice and the two valves will open and close simultaneously.

Cam shaft 29 is driven, by suitable gearing'or sprocket wheels and a chain, directly from the crank shaft so that it rotates at half the speed of said crank shaft and the cams are set so that the valves are lifted so as to admit gaseous fuel into the chamber of the pumping cylinder, on each downward or outward stroke of piston 12.

The two inlet valves to the pump cylinder are centered on a line parallel with the axis of the cam shaft, and there are two cams in the circumferential plane of the cam shaft rotation and in the plane to which one of the valves of the pair to one pump cylinder are located. Each of the two cam lobes occupy one plane in the direction of cam shaft rotation, in lobe length circumferentially of the cam shaft, approximately 90' degrees, or A of the cam circumference. Since 90 degrees of the cam shaft rotation, which is at one engine speed in ratio to the crank shaft isequivalent to 180 degrees of the crank rotation, then each of the two cam lobes in one plane circumferentially, will hold one valve open for the entire suction stroke of the pump piston to which itis attached. Thus each cam lobe may have sufficient circumferential length to hold the valve open for whatever lag in valve closing after the end of the suction stroke, the engine designer or builder may desire.

The bodies of the two Cam lobes in one plane circumferenti'al'ly of the cam shaft will occupy approximately two directly opposite positions on the face of the base circle of the camshaft, thus causing each valve to be opened for the entire duration of each outward or suction stroke of the piston within the pump or precompression cylin der, but during one suction stroke of the piston, one of the two cams in one plane circumferentially, will actuate the valve to which it is adapted and during the succeeding suction stroke of the pump piston, the other of the two cams in one circumferential plane on the cam shaft will actuate the same valve. The cam lobes of the two sets in two circumferential planes and adapted for the actuation of the two valves, are in' pairs, in a line respectively, in a plane parallel with the axis of the cam shaft.

This particular arrangement produces several desirable and advantageous mechanical results, for instance; it is well understood by those familiar with the art of high speed engine design, that, in order to obtain maximum engine power at high engine speed or crank shaft revolutions, the valves must be made to follow closely the line of the cam lobe, the latter being designed to open the valve through a period of a given number of degrees of crank shaft rotation, and then to permit the valve to be closed by spring tension on the deceleration side of the cam lobe so as to producebest volumetric efficiency. If, after a certain design of the cam lobe has been ascertained and provided to the combustion chamber of a two stroke cycle internal combustion engine, it is necessary that the inlet valve function be p'ro-' vided at I to 1 ratio with the crank shaft speed, so that, in an admission period to each pump cylinder during each outward stroke of the piston therein, a sii'ig'l'e cam lobe for each valve arranged in a plane with} said valve circumferentiall'y and operated at engine s eed and with a 180 degree or one-half the base circle of the cam shaft circumference,will hold the valve open dur-' ing each outward stroke of the said pump cylinder piston: Now, it is'als'o understood, that in order to eliminate vibration and twisting of the cam shaft, a considerable diameter must be given to said cam shaft; to provide rigidity and increase of diam eter, obviously increases circumference; If the cam shaft is operated atengine speed, the peripheral speed of the cam lobe and the base circle will be excessive, so therefore, it is intended by this invention, to operate the cam shaft at one-half engine speed and to provide two cam lobes in the same circumferential plane, the use of a cam shaft of relatively greater diameter with less periphery speed and less friction.

Itwi'll be understood that minor changes in the size, form and construction of the various parts of my improved internal combustion engine may be made and substituted for those herein described, without departing from the spirit of the invention, the scope of which is set forth in the appended claims.

I claim' as my iin ention':

1. In a two stroke cycle internal combusti'on' engine, a pumping cylinder, a piston within said pumping cylinder, a crank shaft, a cam shaft, driving means between the crank shaft and the cam shaft whereby the cam shaft is rotated at one-half crank shaft speed, an inlet valve for the pump cylinder, two cam lobes arranged on the camshaft in the same circumferential plane and centered in direct line with the axisof the stem of said' valve, one cam lobe being adapted to open said inlet valve during the period of every other outward stroke of the piston within the pump cylinder and the second cam l'obe' in the same circumferential plane being adapted to open said valve during the period of the alternating outward stroke of said piston within the pumping cylinder.

2. The combination in a two stroke cycle internal combustion engine, of a charge volume pumping cylinder, a. piston Within said pumping cylinder, a crank shaft, a cam shaft, said cam shaft having two lobes arranged in one circumferential plane and spaced exactly opposite the other, or 180 apart for each inlet valve to the pump cylinder for the actuation of the opening function of the charge Volume inlet valve to the pumping cylinder for the full period of each outward stroke of the piston within said pumping cylinder and a driving connection between the cam shaft and the crank shaft to effect rotation of the cam shaft at exactly one-half crank shaft speed.

In testimony whereof I affix my signa- 20 ture. 4

EVERETT R. BURTNETT. 

